H. Kawahara et. al. have reported a liquid phase deposition method which can grow the SiO.sub.2 under less than 50.degree. C. condition in the J. Electronchem Soc., 1988, Vol. 135, no.8, pp2013-16. This method obtained the U.S. Pat. No. 5,073,408. It was originally used to grow the cover film of the glass substrate which will prevent the Sodium ion existing in the glass from dispersing outwardly and avoid destroying the grown liquid crystall display(LCD) on the surface of to substrate. This LPD method provides advantages including simple facility, inexpensive manufactured cost, low-temperature preparation process and the grown Silicon oxide film possess good quality. In addition, it possesses selective deposition capability.
In conventional, the preparations of the poly-Si and poly-Si.sub.1-x -Ge.sub.x film transistor were studied elsewhere, T.J. King et.al. depicted the application of the low pressure chemical vapor deposition (LPCVD) in IDEM Tech. Dig., 1990, pp. 253-256. At first, a amorpous silicon film layer deposed on the surface of glass under the low temperature condition, and then the annealing treatment last for 24 to 72 hours, finally, the poly-Si can be formed. This method spent much more time, not only raising the manufactured cost but accumulating a lot of energy within the products. In addition, the growth chamber cleanness of the general LPCVD system is bad, thus, the quality of the grown poly-Si and poly-Si.sub.1-x -Ge.sub.x could not compare with that of grown in the ultrahigh vacuum chemical vapor deposition (UHV/CVD) system. Although the laser annealing treatment can be used for making the amorphous Si to be the poly-Si under the low temperature. However, the prepared poly-Si film transistor using this method possesses good characteristics, the whole uniformity and the feasibility of the mass manufacture still have some problems that should be further solved. Therefore, the laser anneal method is not a complete method yet until now. On the other hand, a developed latest method that is assisted by the catalyzer is applied for the poly-Si growth, the metal wire is loaded into the cold wall growing chamber and heated to the growth temperature, and then the conventional LPCVD system is adapted, the annealing treatment step can be omitted.
In this invention, the usefulness of the ultrahigh vacuum chemical vapor deposition(UHV/CVD) and chemical mechanical polishing (CMP) systems to fabricate directly the polycrystalline silicon (poly-Si) and polycrystalline silicon-germanium (poly-Si.sub.1-x -Ge.sub.x) thin film transistors under low temperature, 550 .degree. C. and the CMP system is used also for improving the surface morphology.
The main purpose of this invention is to provide a novel method for fabricating the poly-Si and poly-Si.sub.1-x -Ge.sub.x thin film transistors at low temperature and low thermal budget. And the high performance poly-Si and poly-Si.sub.1-x -Ge.sub.x transistors can be prepared without any anneal treatment step.